(19)

(11)

EP 2 286 059 A2

(12)

(88) Date of publication A3: 14.01.2010 (43) Date of publication: 23.02.2011 Bulletin 2011/08 (21) Application number: 09725905.5 (22) Date of filing: 27.03.2009

(51) International Patent Classification (IPC):  E21B 31/08(2006.01) E21B 37/00(2006.01) (86) International application number: PCT/US2009/038552 (87) International publication number: WO 2009/120957 (01.10.2009 Gazette 2009/40)

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK TR Designated Extension States: AL BA RS (30) Priority: 26.03.2009 US 163685 P 27.03.2008 US 40099 P (71) Applicant: M-i Drilling Fluids Uk Limited Aberdeen, Scotland AB10 1UD (GB)	(72) Inventors: WOLF, John, C. Houston TX 77088 (US) TELFER, George Aberdeen Scotland AB25 2RE (GB) ATKINS, James Aberdeen Scotland AB10 6XX (GB) (74) Representative: Giovannini, Francesca et al Osha Liang 32, avenue de l'Opéra F-75002 Paris F-75002 Paris (FR)